Progressive Distributor - On the same wavelength

On the same wavelength

by Paul Markgraff

Sonic and laser measuring tools have distinct advantages and disadvantages. The right tool for the job depends on several factors.

For decades, contractors requiring accurate distance measurements have used simple tools: rulers, yard sticks, tape measures. They are accurate and generally compact, making them easy to use and relatively inexpensive.

With the advent of the microprocessor and integrated circuit, measuring tools began to change. Today, tape measures with digital readouts, sonic measuring tools and laser measuring tools are common tools of the trade, and most contractors are familiar with how they work.

But what some contractors don’t realize is all measuring tools are not created equal. Laser measuring tools are very accurate at long distances. Sonic measuring tools are pretty accurate, but at much shorter distances.

Distributors need to understand the advantages and limitations of these measuring tools so they can help their customers select the right tool for the job.

Sound principles
Sonic measuring tools emit an ultrasonic burst some call a chirp. This burst operates at about 60 kHz. To get an idea of how high this frequency is, human hearing cuts off at about 16 kHz for a person with average hearing.

The ultrasonic chirp exits the sonic measuring tool traveling around 332 meters per second, hits an object and returns to the measuring tool. The tool detects the sound wave on its way back and measures the amount of time it took for the chirp to leave the unit and return. The unit performs a very simple calculation and delivers the distance data to a digital display.

Sonic measuring tools are not extraordinarily accurate. At 30 feet, sonic measuring tools can be off by as much as half an inch plus or minus 1 percent. That doesn’t sound like a lot, but for people requiring precise measurements, 1.5 inches can cause problems. At distances above 50 feet, accuracy degrades quickly.

“Sound can be effected to some degree by air pressure, to a large degree by temperature and to some degree by humidity,” says Chuck Heger, chief technology officer for sonic measuring tool manufacturer Zircon. “Air temperature can significantly alter a sound wave. The warmer the air, the faster the sound wave moves through it. It is significant enough that you need to make a correction for extremely hot or cold air.”

Other inaccuracies from sonic measuring tools result from the design of the product and the nature of the sound wave. When the chirp emerges from the unit, picture the information spreading out like a flashlight’s beam. This cone of information may strike something else and return to the unit before it hits the surface you want to measure. This can return bad information and create problems for the operator.

The greatest advantage to sonic measuring tools is their price. Some retailers will sell these units for as little as $20. They are great for measuring square footage of empty rooms, but any measurement made in a space with obstacles can be inaccurate.

Step into the light
Laser measuring tools work on a similar premise to sonic measuring tools but use different technology. Not only is the technology more complex, the accuracy of the tools depends on entirely different attributes.

To understand how these tools work, first you have to understand a little bit about the mechanics of light. Light travels one foot in a nanosecond, or one billionth of a second. The laser measuring tool sends out a beam of visible light, which hits the target to be measured, and the processor in the tool calculates the amount of time it took for the light to exit the machine and return to the unit.

These tools are far more accurate than sonic measuring tools. CST/berger sells one model that is accurate to within a quarter of an inch at 100 feet. And the price has come down. Six or seven years ago, a laser measuring tool would have cost as much as $900. Today, big box retailers can sell them for as little as $99.

“A huge benefit of these tools is the ability to measure square footage and volume from one place,” says Mark Gordon, national sales development manager for CST/berger. “In the old days, you would have to stretch out a tape measure to get one measurement, maybe climb over a few obstacles to get from one side of a room to another. With these tools, you can shoot the length and the width with very little maneuvering and the unit will perform the calculation for you.”

Visible light lasers do have disadvantages though. On a bright, sunny day, the laser can be very difficult to see. When the target area is very darkly colored or highly reflective, visible laser dots can be tough to find. Laser measuring tool manufacturer RoboToolz has overcome this by offering a laser measuring tool that uses an infrared laser for measurement, a visible laser for pointing and a reflective target users can set up for measuring at longer distances.

“There are two advantages to infrared lasers,” says Daniel Hill, vice-president of sales and marketing for RoboToolz. “The first is it stays out of the visible light spectrum, so sunlight has no effect on the measuring laser. The other advantage is the pulse technology we employ with our infrared laser. These pulses are large packets of energy the unit can easily find, making it extremely accurate at long distances.”

According to RoboToolz, its infrared unit is accurate up to 1/8th of an inch at 200 meters. However, at shorter distances, the advantages of infrared are negligible. It will work at least as well as visible laser measuring tools. And, infrared tools are basically as expensive as visible laser tools.

Understanding the accuracy requirements of the job and the advantages and disadvantages of these various sonic and laser measuring tools will go a long way toward helping end-users purchase the right tool for the job.